Eye tissue measurements

ABSTRACT

A compact system for performing laser ophthalmic surgery is disclosed. The systems and methods may be used to measure corneal thickness or other anatomy to prepare a treatment plan for any of numerous treatments, such as LASIK, PRK, intra stromal lenticular lens incisions, cornea replacement, or any other treatment. By using a reduced power femtosecond laser backscatter may be measured to calculate distances such as distances between an interior boundary and an exterior boundary of a cornea or other tissue.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of and claims priority under 35U.S.C. § 120 to U.S. patent application Ser. No. 15/699,963, filed Sep.8, 2017, which claims priority to, and the benefit of, under 35 U.S.C. §119(e) of U.S. Provisional Appl. No. 62/385,167, filed Sep. 8, 2016. Theabove referenced applications are incorporated herein by reference inits entirety their entireties.

TECHNICAL FIELD

Embodiments of this invention generally relate to the field of eyesurgery, and more specifically to eye tissue measurements using anophthalmic laser system.

BACKGROUND

Vision impairments such as myopia (near sightedness), hyperopia (farsightedness), and astigmatism can be corrected using eyeglasses orcontact lenses. Alternatively, the cornea of the eye can be reshapedsurgically to provide the needed optical correction.

Eye surgery has become commonplace with some patients pursuing it as anelective procedure to avoid using contact lenses or glasses to correctrefractive problems, and others pursuing it to correct adverseconditions such as cataracts. And, with recent developments in lasertechnology, laser surgery is becoming the technique of choice forophthalmic procedures. The reason eye surgeons prefer a surgical laserbeam over manual tools like microkeratomes and forceps is that the laserbeam can be focused precisely on extremely small amounts of oculartissue, thereby enhancing accuracy and reliability of the procedure.These in turn enable better wound healing and recovery followingsurgery.

Different laser eye surgical systems use different types of laser beamsfor the various procedures and indications. These include, for instance,ultraviolet lasers, infrared lasers, and near-infrared, ultra-shortpulsed lasers. Ultra-short pulsed lasers emit radiation with pulsedurations as short as 10 femtoseconds and as long as 3 nanoseconds, anda wavelength between 300 nm and 3000 nm. Examples of laser systems thatprovide ultra-short pulsed laser beams include the Abbott Medical OpticsiFS Advanced Femtosecond Laser, the IntraLase FS Laser, and OptiMedica'sCatalys Precision Laser System.

Current surgical approaches for reshaping the cornea include laserassisted in situ keratomileusis (hereinafter “LASIK”), photorefractivekeratectomy (hereinafter “PRK”) and Small Incision Lens Extraction(hereinafter “SMILE”).

In the LASIK procedure, an ultra-short pulsed laser is used to cut acorneal flap to expose the corneal stroma for photoablation withultraviolet beams from an excimer laser. Photoablation of the cornealstroma reshapes the cornea and corrects the refractive condition such asmyopia, hyperopia, astigmatism, and the like.

Traditionally, to measure various tissues within an eye to determine atreatment plan, surgeons would measure the thickness of an eye tissue,such as a cornea by manually placing an ultrasound device on the eye indifferent places, manually. This methodology can be cumbersome. Hence,there is a need for improved systems and methods of measuring eyetissues without resorting to manual methods.

SUMMARY

Hence, to obviate one or more problems due to limitations anddisadvantages of the related art, this disclosure provides systems andmethods for use in suitable ophthalmic laser surgery systems.Embodiments as described herein provide improved methods and apparatusto facilitate ophthalmic surgical procedures for the eye.

Embodiments of Methods and systems described here include measuringcorneal thickness, including generating a femtosecond pulsed laser beamof less than 40 milliwatts in power, directing the laser beam into thecornea of an eye of a patient, the cornea having an interior side towarda center of the eye and an exterior side, focusing the directed laserbeam to a focus point beyond the cornea interior into the eye, movingthe focus point of the laser beam through the cornea toward the exteriorside of the cornea, moving the focus point of the laser beam past theexterior side of the cornea, receiving a backscatter of the laser beamas the focus point moves, determining a time corresponding to thereceived backscatter of the laser beam as the focus point moves,calculating a distance between the cornea interior and cornea exteriorbased on the received backscatter and corresponding time as the focuspoint moves.

Embodiments of the invention include the laser beam having a wavelengthbetween 300 nm and 1200 nm. Embodiments may also include the laserhaving a wavelength between 1020 and 1040 nm. Embodiments may furtherinclude the laser beam having a numerical aperture NA between 0.3 and1.3.

Embodiments of the invention include a polarized laser beam. Embodimentsmay include the laser beam having a pulsed laser beam having a pulseduration between 10 femtoseconds and 10 picoseconds.

Systems and methods here include docking a femtosecond laser patientinterface to a cornea of a patient, attenuating the femtosecond laserpower to a level for measuring, wherein the attenuated femtosecond laserhas a power at the focus point of less than 40 milliwatts, focusing thefemtosecond laser to a beam at a focal point in the interior side of thecornea of the patient in x lateral axis, y lateral axis and a z depthaxis, moving the femtosecond laser focal point in the z axis from theinterior side of the cornea through the cornea and toward an exteriorside of the cornea, capturing a backscatter of the femtosecond laserfocal point as it moves in the z axis from the interior side of thecornea to the exterior side of the cornea, and recording a time thefemtosecond laser focal point moves in the z depth axis from theinterior side of the cornea to the exterior side of the cornea,calculating a power of the captured backscatter as the laser focal pointmoves in the z depth axis from the interior side of the cornea to theexterior side of the cornea, determining a cutting distance, based onthe recorded time the laser focal point moves and the calculated powerof the captured backscatter, powering up the femtosecond laser from themeasuring power to an incision power, incising the cornea at thedetermined cutting distance in the cornea to remove a portion of thecornea. Alternatively or additionally, the cutting distance is 50 μmfrom an endothelium layer of the cornea. Alternatively or additionally,the systems and methods may include determining, from the capturedbackscatter, a folded shape of the cornea while the patient interface isdocked, wherein the incision on the cornea at the determined cuttingdistance follows the folded shape of the docked cornea. Alternatively oradditionally, the incision following the folded shape of the corneawhile docked does not incise an endothelium layer in the cornea.Alternatively or additionally, the laser has a wavelength between 1020nm and 1040 nm. Alternatively or additionally, the laser has awavelength between 335 nm and 400 nm. Alternatively or additionally,wherein the laser beam has a numerical aperture NA between 0.3 and 1.3.Alternatively or additionally, the laser beam is polarized.Alternatively or additionally, the laser beam is a pulsed laser beamhaving a pulse duration between 10 femtoseconds and 10 picoseconds.

This summary and the following detailed description are merelyexemplary, illustrative, and explanatory, and are not intended to limit,but to provide further explanation of the embodiments as claimed.Additional features and advantages of the embodiments will be set forthin the descriptions that follow, and in part will be apparent from thedescription, or may be learned by practice of the embodiments. Theobjectives and other advantages of the embodiments will be realized andattained by the structure particularly pointed out in the writtendescription, claims and the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the embodiments are set forth with particularityin the appended claims. A better understanding of the features andadvantages will be facilitated by referring to the following detaileddescription that sets forth illustrative embodiments using principles ofthe embodiments, as well as to the accompanying drawings, in which likenumerals refer to like parts throughout the different views. Like parts,however, do not always have like reference numerals. Further, thedrawings are not drawn to scale, and emphasis has instead been placed onillustrating the principles of the embodiments. All illustrations areintended to convey concepts, where relative sizes, shapes, and otherdetailed attributes may be illustrated schematically rather thandepicted literally or precisely.

FIGS. 1A and 1B are simplified diagram views of a surgical ophthalmiclaser system according to certain embodiments.

FIGS. 2A and 2B are simplified views of an optical field according tocertain embodiments.

FIG. 3 is a diagram of a pulsed laser beam according to certainembodiments.

FIG. 4 is a graph related to laser beam optimization according tocertain embodiments.

FIG. 5 illustrates resonant scanners according to certain embodiments.

FIG. 6 is a graph related to resonant scanning operation according tocertain embodiments.

FIG. 7 illustrates a schematic view of a beam delivery system accordingto certain embodiments.

FIG. 8 illustrates a schematic view of a scanner according to certainembodiments. As shown in FIG. 8, the laser is synchronized with thescanner. The laser beam is shut-off when the scanner approaches the maxangle (zero velocity) to avoid overlapping focus spots in successivepulses.

FIG. 9 is a table of scanner parameters according to certainembodiments.

FIG. 10 illustrates a perspective view of a scanner system according tocertain embodiments.

FIG. 11 illustrates a perspective and graphical view of a scan linerotator according to certain embodiments.

FIGS. 12A-12C illustrate various patient interfaces used with certainembodiments.

FIG. 13 illustrates a patient interface according to certainembodiments.

FIGS. 14A-14B illustrate beam splitter optics according to certainembodiments.

FIG. 15 illustrates a table of visualization parameters according tocertain embodiments.

FIG. 16 illustrates beam splitter optics according to certainembodiments.

FIG. 17 illustrates an example corneal back scatter pattern according tocertain embodiments.

FIG. 18 illustrates an example system measuring a corneal thicknessaccording to certain embodiments.

FIG. 19 illustrates an example corneal backscatter power plot accordingto certain embodiments.

FIG. 20 illustrates an example corneal thickness map according tocertain embodiments.

FIG. 21 illustrates an example corneal thickness wrinkle correctable bycertain embodiments.

FIG. 22 illustrates an example corneal thickness wrinkle correctable bycertain embodiments.

DETAILED DESCRIPTION

Embodiments of this invention are generally directed to systems andmethods for laser-assisted ophthalmic procedures.

Referring to the drawings, FIG. 1A shows an ophthalmic surgical lasersystem 1 for making an incision in a target material such as a cornea ofan eye. A laser 2 may comprise a femtosecond laser capable of providingpulsed laser beams, which may be used in optical procedures, such aslocalized photodisruption (e.g., laser induced optical breakdown).Localized photodisruptions can be placed at or below the surface of thematerial to produce high-precision material processing. The laser may bea micro-chip picosecond laser. For example, a laser beam delivery systemmay be used to scan the pulsed laser beam to produce an incision in thematerial, create a flap of material, create a pocket within thematerial, form removable structures of the material, and the like. Theterm “scan” or “scanning” refers to the movement of the focal point ofthe pulsed laser beam along a desired path or in a desired pattern.

Although the laser system 1 may be used to photoalter a variety ofmaterials (e.g., organic, inorganic, or a combination thereof), thelaser system 1 is suitable for ophthalmic applications. For example, thefocusing optics direct the pulsed laser beam toward an eye (for example,onto or into a cornea) for plasma mediated (for example, non-UV)photoablation of superficial tissue, or into the stroma of the corneafor intrastromal photodisruption of tissue.

The system 1 includes, but is not limited to, a laser source 2 capableof generating a pulsed laser beam, a resonant scanner 3 for producing afast scan line or raster 12 of the pulsed laser beam, an XY scan device4 or scan line rotator (e.g., a Dove prism, Pechan prism, or the like)for rotating the scan line 12, a beam expander 5, an objective 6, amoveable XY stage 7 for deflecting or directing the pulsed laser beamfrom the laser 1 on or within the target, a fast-Z scan device 8, apatient interface 9 that may include a visualization beam splitterinside a cone, an auto-Z device 10 for modifying the depth of the pulselaser beam and providing a depth reference, an optical path 11, acontroller 13, and a communication module 15. An imaging video cameramay further be included.

The laser beam delivery system of the system 1 delivers a pulsed laserbeam at a focal point of a target in a patient's eye in a raster patternand may include the resonant scanner 3, beam expander 5, objective 6 andpatient interface 9.

The focal point of the target in the patient's eye may include one ormore of a cornea, stroma, capsular bag, crystalline lens, and zonule.The pulsed laser beam may modify the target in the patient's eye toproduce corneal tissue modification such as corneal cross-linking. As aresult of the pulsed laser beam, a desired incision may be produced inthe patient's eye.

The resonant scanner 3 generates a fast scan line at a fixed resonantfrequency. The resonant scanner 3 may produce a raster between 1 mm and2 mm where a width of the scan line may be adjusted. A resonant scannerscans very fast and produces a one-dimensional scan that is, forexample, a horizontal line.

The XY scan device 4 or scan line rotator moves the pulsed laser beamraster 12 in a lateral direction so as to rotate the scan line to anydesired orientation on an XY plane. For example, a Dove prism or Pechanprism rotates the raster to any direction on an XY plane such as a scanline perpendicular to the XY device 7 trajectory to provide scancoverage over a larger area.

The XY scan device 7 is a movable XY scanning stage having a finalfocusing objective 6 mounted thereon. The XY scan device 7 carries thefinal objective 6 to move the fast scan line to cover an entiretreatment area. The movable XY scanning stage 7 may include a recoillessstage configured to reduce or eliminate mechanical vibration. The XYscanning stage 7 is configured to move the pulsed laser beam in alateral direction such that the laser beam may cover an entire surgicalfield of the patient's eye. Accordingly, the scan line rotator 4modifies an orientation of the scan line while the moveable XY scanningstage moves the optical field of the scan line across an XY plane.

The fast Z scan device 8 modifies a depth of focus of the pulsed laserbeam and may provide fine depth control. The fast Z scan device 8 mayeither be set at a fixed position or run dynamically to correct thesystem's inherent depth variations at different (X,Y) locations. In thelatter case, a fast Z position is determined by the XY trajectory anddoes not affect the XY trajectory. A fast Z scan sets a cut depth andmoves the focus in the depth direction to produce, for example, aside-cut in a target material.

A shutter (not shown) can be kept open during a bed cut or may becontrolled to open/close to block the unwanted pulses during a bed cut.

The patient interface 9 couples the patient's eye to the ophthalmicsurgical laser system 1. The patient interface design has a fixed conenose on the system. The disposable part of the patient interface issingle-piece device that allows the use of flat applanation, or the useof liquid interface, for patient sitting upright, respectively. Anydesign with a separated suction ring does not apply for a patientsitting upright. The patient interface 9 may include a visualizationbeam splitter in the cone of the patient interface. A beam splitter isplaced inside this cone to allow the full eye to be imaged viavisualization optics. This allows the system to be made smaller. Thepatient interface may be removed when an eye-tracking system is used.Visualization may be provided through, for example, a video microscopeor ocular microscope.

The auto Z module 10 measures a distal end surface of a lens cone of thepatient interface coupled to the patient's eye and provides a depthreference for the Z scan device 8 of the ophthalmic laser system. Theauto Z module 10 uses the focus of a surgical beam as the measurementprobe, so there is no need to calibrate the measurement reference andthe laser focus, which is otherwise required for other depth measurementmethods, such as optical coherence tomography (OCT).

The controller 13 is operably coupled with the laser delivery system,the XY scan device 4, the Z scan device 8, detector 14 and thecommunication module 15. The controller 13 is configured to direct thelaser delivery system to output the pulsed laser beam in a desiredpattern at the focal point of the target in the eye so as to modify thetarget.

The controller 13, such as a processor operating suitable controlsoftware, is operatively coupled with the components of the system 1 todirect a fast scan line 12 of the pulsed laser beam along a scan patternon or in the target material.

In some embodiments, the system 1 includes a beam splitter within thepatient interface 9 and a detector 14 coupled to the controller 13 forclosed-loop feedback control mechanism (not shown) of the pulsed laserbeam. Other feedback methods may also be used, including but notnecessarily limited to position encoder on the scanner 3 or the like.

In one embodiment, the pattern of pulses may be summarized inmachine-readable data of tangible storage media in the form of atreatment table. The treatment table may be adjusted according tofeedback input into the controller 13 from an automated image analysissystem in response to feedback data provided from an ablation monitoringsystem feedback system (not shown). Optionally, the feedback may bemanually entered into the controller 13 by a system operator.

The feedback may also be provided by integrating a wavefront measurementsystem (not shown) with the laser surgery system 1. The controller 13may continue and/or terminate at least one incision in response to thefeedback, and may also modify the planned sculpting based at least inpart on the feedback. Measurement systems are further described in U.S.Pat. No. 6,315,413, the entire disclosure of which is incorporatedherein by reference.

The communication module 15 provides information to the operator of thelaser system 1 at the system and/or remotely via wired or wireless dataconnection. The communication module 15 may include a display device andinput/output devices as known in the art to display information to anoperator. An operator may control the system 1 via any known inputcontrol system including but not limited to a keyboard, a mouse, voicecontrol, a motion sensing system, a joystick, and an eye-trackingsystem. The system 1 may be operated remotely and may also be monitoredand serviced remotely.

In another embodiment, FIG. 1B shows the beam delivery optics of asystem 20. The system 20 includes, but is not limited to, an inputpulsed laser beam 21 from laser source (not shown), fast-Z scan 22, aresonant scanner 23 for producing a fast scan line 30 of the pulsedlaser beam 21, a scan line rotator 24 (e.g., a Dove or Pechan prism, orthe like) for rotating the scan line 30, a beam expander 25, anobjective 26 with an adjustable Z-baseline (slow-Z scan) 26, a moveableX-Y stage 27 for deflecting or directing the pulsed laser beam 21 on orwithin the target, a patient interface 28 that may include a beamsplitter, an optical path 29, a controller 31, a detector 32, and acommunication module 33. The slow-Z scan 26 sets the focus at a fixeddepth and may set the Z-baseline. For example, the slow-Z scan 26 isstationary during a bed cut.

Some embodiments of the system are compact desktop systems that areplaced on a table or the like. Other embodiments may include a motorizedstage. The compact system allows a patient and patient interface to beoriented downwards, upwards, or in any direction, and not necessarilyupright.

Next, FIG. 2A provides a simplified view of a surgical field 40.Typically, laser-assisted ophthalmic procedures are performed within asurgical field 40 of an eye that has a diameter of about 10 mm. Some ofthese systems utilize solid state femtosecond lasers including anoscillator, stretcher, amplifier and compressor. Conventional lasersystems include a laser with optics large enough to generate a laserbeam with an optical field that matches the surgical field. Scanningmirrors or other optics (not shown) may be provided to angularly deflectand scan the pulsed laser beam over the entire surgical field. Thesescanning mirrors may be driven by a set of galvanometers that furtheradd to the bulk and complexity of conventional laser systems.

However, providing a sufficient numerical aperture (NA) to perform lasersurgery requires large, expensive optics and a corresponding cumbersome,heavy and expensive beam delivery system. For example, an objective ofthe iFS Advanced Femtosecond Laser System alone weighs over 30 lbs. inorder to allow a pulsed laser beam to scan freely within the 10 mmsurgical field. These systems provide a practical maximum NA of about0.4 due to the increasing cost, size and complexity of system componentswhen NA is increased.

FIG. 2B illustrates an optical field 42 according an embodiment of theembodiments that are significantly smaller in diameter than the surgicalfield 41. The diameter of the optical field 42 depends on the length ofthe fast scan line 12 generated by the resonant scanner 3. For example,the diameter of the optical field 42 may be between 1 mm and 2 mm, andmay preferably be 1.2 mm. This allows the laser to be made much smallerwith laser beam tissue interaction in a low-density plasma mode.

For a given NA, the size and cost of the laser optics is reduced as theoptical field is reduced in size. Consequently, increasing an NA valueis significantly more cost effective for a smaller optical field. Sincethe optical field 42 may be about five to ten times smaller than thesurgical field 41, a higher NA is achievable at a reduced cost comparedto an optical field matching the surgical field 40. Accordingly, theembodiments provides higher NA at lower cost.

As shown in FIG. 2B, an optical field 42 does not by itself cover anentire surgical field 41. However, the optical field 42 is movedmechanically by the moveable XY device 7 across the entire surgicalfield 41. As will be described later, a resonant scanner 3 generates avery fast scan line within the optical field 42 that is oriented(rotated) within the optical field 42 by an XY scan device 4 and movedwithin the entire surgical field 41 by the moveable XY scan device 7.Reducing the size of the optical field significantly reduces thecomplexity, size, and weight of the laser source. Furthermore, anopto-mechanic arm mechanism is unnecessary in the laser system 1. Inthis manner, the laser optics are provided at a much lower cost withimproved focus to achieve better surgical outcomes.

Embodiments of the embodiments may utilize a femtosecond oscillator oroscillator low energy laser. The laser source 2 may include an activemedium fiber laser amplifier, oscillator and compressor, but need notinclude a stretcher. The laser source 2 may be fiber oscillator based,such as a diode-pumped fiber laser. The diode-pumped fiber laser may bea mode-locked fiber oscillator based laser having a single-mode,double-clad fiber oscillator and all positive dispersion elements.

The laser may generate a pulsed laser beam having a pulse repetitionrate in the range between 5 MHz and 40 MHz, pulse energy in the rangebetween 1 nJ and 5 μJ, a wavelength between the range of 1020 nm and1065 nm, a pulse duration between the range of 10 femtoseconds and 10picoseconds, a spot size between 0.2 μm and 2.0 μm (FWHM), and anumerical aperture NA between 0.25 and 1.3. An NA of 0.6 produces a 1.1μm FWHM spot. The NA value is preferably provided between 0.25 and 1.0,more preferably between 0.4 and 1.0, and may be 0.6 in the illustratedexamples.

Moreover, the reduction in size and complexity of the system 1 allowsthe laser delivery system to be configured to deliver the pulsed laserbeam to the focal point of the target in the patient's eye while thepatient is seated either in an upright position or in a recliningposition.

FIG. 3 is a diagram of a pulsed laser beam 50 including the relationshipbetween the beam diameter, pulse energies, focus spot diameters andeffective focal length. The focus spot 51 generated by a laser 2 may beprovided at a focus point of the cornea to generate a bubble thatseparates and dissects tissue.

A pulsed laser beam directed at corneal tissue will first generateplasma. Additional pulses then generates a bubble in tissue. Finally,the bubble expands to generate tissue separation/dissection.

A pulsed laser beam applied to tissue first generates plasma, which thengenerates a bubble, and finally leads to tissue separation/dissection. Atypical threshold value for tissue dissection is 10¹³ W/cm². To performtissue dissection, a pulsed laser beam needs to reach or exceed thisthreshold value determined by the equation ε/τσ, where ε is the energyof the beam, τ is the pulse width, and σ is the area of the beam.

Based on this relationship, for a given amount of energy, decreasing thespot size will increase the optical density of the beam since the sameamount of beam energy is concentrated in a smaller area. Likewise, asthe spot size of the beam decreases, the amount of energy of the beammay be reduced while still exceeding the tissue dissection thresholdvalue. A smaller amount of beam energy applied in a smaller area resultsin a finer tissue cut.

An inverse relationship exists between spot size and numerical aperturesuch that as NA becomes larger, a spot size 51 becomes smaller.Numerical aperture represents the sine of the half angle of the cone ofa laser beam. Accordingly, a higher NA value is desirable in providing afiner cut.

For example, the laser system 1 outputs an energy level of 0.14 ρJ thatis 20% of the energy level output of 0.7 ρJ from the iFS Laser System.Similarly, the system 1 provides a pulse width of 120 fs and area ofπ·0.5² μm² while the iFS Laser System provides a pulse width of 600 fsand area of π·0.8² μm².

FIG. 4 is a graph 60 related to laser beam optimization. As illustratedin FIG. 3, a beam diameter 52 may be different from the diameter of alens 53 that focuses the light pulse into a focus spot 51. Selection ofa beam diameter 52 smaller than the lens diameter 53 ensures that all ofthe light energy passes through the lens. However, an inverserelationship exists between a beam diameter and a focus spot size suchthat the focus spot size will increase as the beam diameter decreases.F_(PEAK) represents energy area density and T represents energytransmission.

Similarly, laser overfield is a configuration where the beam diameter 52is greater than the lens diameter 53 such that a portion of the lightenergy is not transmitted through the lens and lost. But, the loss inenergy efficiency by laser overfield provides the benefit of a smallerfocus spot size 51.

In balancing the factors of energy efficiency and spot size, FIG. 4illustrates the optimal conditions to attain maximum energy density. Inparticular, a maximum peak fluence is achieved with about a 10% loss oftransmission. In other words, the optimum ratio of energy transmissionto spot size occurs when the pulsed laser beam diameter is about 10%larger than the lens diameter.

A laser as described above may operate at very high frequencies such ason the order of 10 MHz (or 10,000,000 pulses/sec). Laser pulses that arenot scanned will be directed at a single point which is unsuitable forophthalmic procedures. Therefore, a scanner is needed to operate at asufficient frequency to scan these pulses across a surgical area.

The scanner 3 of the system 1 may be a high frequency resonant opticalscanner having a fixed frequency in a range between 3500 Hz and 21,000Hz. In an preferred embodiment, a 7910 Hz resonant scanner isimplemented. Use of a resonant scanner is particularly effective as theyhave no wearing parts, are reliable, cost-effective and compact (e.g.,1.0″W×0.7″D×2.5″H). The resonant scanner 3 produces a line rasterpattern with a length of the raster pattern between 0.5 mm and 2 mm. Insome embodiments, the resonant optical scanner is configured to scan thepulsed laser beam from the laser delivery system in a line.

FIG. 5 illustrates exemplary resonant scanners 70 and 71 that include amirror attached to a metal rod that vibrates at an inherent resonantfrequency. The shape and composition of the rod are selected to operateat a desired frequency to scan laser pulses. The resonant scanner 3 doesnot require a plurality of mirrors or a set of cumbersome galvos to scanacross a surgical field as other systems do. Instead, the scan line maybe rotated by a scan line rotator within an optical field and thescanner 3 may be scanned across a surgical field by a moveable XY stage.In some embodiments, the resonant scanner 3 provides an order ofmagnitude in weight and cost savings over the scanner system provided inthe iFS Laser System. The resonant scanner 3 may scan at a rate of about20 m/s while the iFS scanner scans at a rate of about 3 m/s.

As illustrated in the graph 80 of FIG. 6, the scanning provided by aresonant optical scanner 3 is characterized by a sinusoidal curve. The aresonant optical scanner may oscillate at a frequency between 200 Hz and21000 Hz. The curve 81 represents the scanning angle of a resonantscanner 3 and curve 82 represents the scanning speed. As shown by thecurve 82, the scanning speed continually varies such that the density oflaser spots along the scan line will vary. Accordingly, that thedistribution of laser pulses is uneven.

For instance, scan line 86 illustrates the sinusoidal distribution oflaser spots 87 provided by a resonant scanner 3. Whether a scanningspeed reaches zero or a maximum speed, laser pulses will continue to beemitted at the same rate. Undesirable spot overlapping 83 occurs whenthe scan speed is at and near zero. This may lead to areas of tissuethat are overcut from an excess number of laser pulses.

Some embodiments overcome this by preventing overlapping spots 83. Inone embodiment, the overlapping spots 83 are emitted but physicallyblocked 84 from scanning a target material to provide a higher qualitytissue cut. During time period 85 between the blocked periods 84, thelaser is not blocked and passes an aperture of the laser system.

FIG. 7 illustrates a schematic view of a beam delivery optics system 90.A pulsed laser beam 91 emitted by a laser source (not shown) reaches aresonant optical scanner 92 and is delivered into a beam expander 93.The beam expander includes a lens 94 that focuses the beam through ascan line rotator 95 and another lens 94. A predetermined portion 97 ofthe beam 91 is blocked by a field stop 96 to limit the scan length ofthe raster.

The pulses 97 may, for example, correspond to the blocked portion 84overlapping spots 83 in FIG. 6. In this manner, undesirable light pulsesare physically blocked within a beam expander 93 as the light focuses,ensuring that laser spots are not concentrated too densely within a spotor scan line area. The blocker or field stop 96 may be provided near butnot precisely at the focal plane so as to prevent the blocker fromburning. It is noted that conventional scanners do not exhibitsinusoidal wave characteristics such that those systems have no need toprovide blocking.

In an alternative embodiment, FIG. 8 illustrates a schematic view of ascanning system 100. A resonant optical scanner 101 is illustrated asvibrating so as to produce a scan line 104. A laser (not shown)producing laser pulses is synchronized with the frequency of the scanner101 such that the laser is turned on 102 and off 103 when the scanner101 approaches a predetermined maximum scan angle with a correspondingzero velocity in order to prevent overlapping focus spots in successivepulses.

Equation 1 is an algorithm for determining a duty cycle that is apercentage time that a beam passes an aperture, scanner frequency,optical peak-to-peak angle, a pupil diameter for given laser pulserepetition rate, and desired numerical aperture of the optical system.An example for NA=0.6 is provided below:

$\begin{matrix}{{2400\mspace{14mu} {{\cos \left( {\frac{\pi}{2}\beta} \right)}\left\lbrack {\theta_{OPTP} \cdot f_{SCAN} \cdot D_{{PUP}II}} \right\rbrack}} \geq f_{LASER}} & \left( {{Eq}.\mspace{14mu} 1} \right)\end{matrix}$

Equation 1 guides the selection of resonant scanner parameters for aspot edge to edge condition, as shown in Table 110 in FIG. 9. Table 110highlights the values that satisfy a requirement of spot size (FWHM=1.1um) and avoiding laser spot overlap.

In some embodiments, a fast raster scanning pattern can be generated bysynchronizing a plurality of resonant scanners in the laser system 1.For example, FIG. 10 illustrates a pair of perpendicular scanningresonant mirrors 120 with the same frequency, the same amplitude, and aphase difference of 90° between them that generate a fast circular scanline 121, for example.

A circular scan line exhibits a number of advantages including equalspot distribution so as to render blocking techniques redundant. In thiscase, the linear speed of the scanning is a constant, and is equal tothe maximum speed that can be achieved with a single scanner. Therefore,there is no need to block the “zero speed” points as in the case ofusing a single scanner, and the duty cycle is 100%, i.e., 100% of laserpulses will be used for tissue dissection. Furthermore, a circular scanline ensures that targeted tissue receives two pulses with each pass,thereby ensuring a cut. Also, a circular scan line is also well matchedagainst another curve, such as the edge of a circular surgical field.

The first scanner may be provided for the x axis while the secondscanner may be provided for the y axis in different phase relation togenerate a plurality of two-dimensional scan patterns that may obviatethe need for a scan line rotator. The use of at least two scanners maygenerate a line oriented at any desired angle, circle, curve, etc.

Another arrangement of synchronization is to synchronize two parallelscanners so that the optical peak-to-peak angle is doubled in comparisonwith a system using one resonant scanner. In yet another embodiment, aplurality of resonant scanners may be synchronized to extend thescanning range of a single scanner.

Next, embodiments of a scan line rotator will be discussed. A resonantscanner produces a one dimensional scan line in a single direction.However, this output is not ideal for cutting near an edge or curve of asurgical field. For example, when an optical field is provided along anedge of surgical field, the line must be rotated to fit the curve.Therefore, a scan line rotator is configured to rotate the scanned linein a desired orientation.

FIG. 11 illustrates a perspective view of an exemplary scan line rotator130 and graphical views of a scan line rotated by a scan line rotator.The scan line rotator 130 is a Dove prism, but may also be a Pechanprism or a set of mirrors. Implementations of a scan line rotator usinga Dove prism or Pechan prism are cost-effective, compact andlightweight, and contribute to a compact laser system. The input scanline 131 is a non-rotated scan line. As the scan line rotator 130rotates by an angle θ, the input scan line 131 will follow the rotationand the output scan line will be rotated by 2θ.

The output raster 133 is thus oriented in any desired direction to scanan entire optical field. In combination with an XY stage, the system 1may scan an entire treatment area. Tissue fibers may sometimes bealigned in certain directions that favor a rotated raster. Furthermore,a scan line rotator allows for flap creation, cornea incisions, IEK,inlays, rings, etc. and procedures such as SmILE or ReLEx procedure.

FIGS. 12A-12C illustrate interfaces which may be employed with thepresent embodiments. For many prior art femtosecond laser workstations,the field of view for visualization optics 184 such as a CCD and videomicroscope is similar to the field of view of surgical beam scanningsuch that a visualization beam splitter 183 is positioned above thefocusing objective 181, patient interface 180, and cornea 185. In thisconfiguration, the size of the optics system, including both beamdelivery 182 and visualization 184, is generally large and unwieldy.

FIG. 12B is a schematic cross-sectional view of the patient interface180 that includes a cone 186 that is fixed to the system, avisualization beam splitter 187, and a disposable patient interface lens188. A beam splitter 187 is coated for reflecting the visual spectrumbut passes light for the femtosecond laser wavelength and is placedinside the cone frame 186 of the patient interface 180 fixed to thesystem. The ocular video microscope optical path goes through this beamsplitter. Accordingly, a cutting process may be viewed and/or displayedin-situ.

FIG. 12C is a cross-sectional view of another patient interface 189where a visualization beam splitter is placed inside the cone of thepatient interface 189. This design is sufficient for a limited range ofnumerical aperture of surgical beam, for example, NA≤0.4. For yetgreater NA, such as NA=0.6, some oblique rays of the surgical beam willexperience high loss at the beam splitting surface (the 45° surface asshown in the diagram). As the NA increases, the size of the beamsplitter will need to increase as well.

The visualization optical path may be provided outside the cone of thepatient interface in a side channel. However, for deep set eyes, theside channel has to be placed much higher, increasing the size and bulkof the beam splitter. Consequently, the outer dimension of the patientinterface cone will not fit the normal anatomy of a patient eye and isthus inadequate based on human factors. Simply put, a user's facialfeatures will occupy the same space as the enlarged patient interfacenecessary to accommodate a visualization beam splitter for high NA lasersystems.

FIG. 13 illustrates a patient interface according to certainembodiments. To overcome the issues described above, a rotatableprotruding portion 192 of the patient interface 190 is rotatable aboutan axis 191 and provided on the temporal side of the patient head toallow the optical image signal 193 to exit the patient interface. To fitboth left and right eyes of a patient, the visualization optics(including the beam splitting optics, the patient interface 190, theimaging optics, and the CCD) are rotated 180 degrees in accordance withtreating left and right eyes, respectively. In this manner, the largervisualization beam splitter elements are better positioned to avoidconflict with a user's face.

FIGS. 14A-14B illustrate beam splitting optics according to certainembodiments. A patient interface 200 is provided including twobeam-splitting surfaces, BG and GP. These two surfaces divide the fullfield of view into left half and right half, and form two separatevisualization channels. As a result, this reduction in the size of thechannels allows the channels to fit into the cone of the patientinterface 200 such that no rotation of the visualization beam splitteris needed when treating left and right eyes. Furthermore, the channelssupport high NA (NA=0.6) surgical beams. FIG. 14B illustrates across-sectional perspective view of the patient interface 210 with avisualization beam splitter in the cone.

An interface for coupling a patient's eye to an ophthalmic surgicallaser system includes a lens cone defining a first plane surface coupledwith a delivery tip of the ophthalmic laser system. The lens coneincludes an apex ring coupled to the first plane surface. The apex ringincludes a distal end including a first receptacle configured to receivean attachment ring, the attachment ring configured to overlay ananterior surface of the patient's eye. The first receptacle and theattachment ring may be disposable. A central cavity is provided toreceive the lens cone. A contact lens may applanate the anterior surfaceof the patient's eye.

One or more beam-splitter optics are provided to allow a pulsed laserbeam to pass through the interface to a focal point of the target in thepatient's eye. The beam-splitter optics may include one or moremulti-facet beam-splitter optics and a side-imaging optical channel thatis configured to rotate to a temporal side of the patient's eye.Alternatively, the beam-splitter optics may include dual imagingchannels. The beam-splitter optics may be provided to manipulatenon-telecentric imaging rays at a full optical cone angle equal to orgreater than fifteen degrees.

FIG. 15 illustrates a table of visualization parameters according to anembodiment of the present embodiments. The specific numerical values forthe half cone angle (α), the beam splitting surface angle (β), and theedge ray incident angle (γ), and the geometry dimensions of thevisualization beam splitter are given in table 220.

FIG. 16 illustrates beam splitting optics according to certainembodiments. The patient interface 230 in FIG. 16 divides the full fieldof view into two halves, images the two halves into two differentoptical channels, and processes to combine the two half-images togetherto reconstruct the full field of view. In this manner, the entirevisualization beam splitting optics can be placed inside the cone of acompact patient interface 230.

This approach of dividing the full field of view into several smallerfields, and then combining the images of the smaller results toreconstruct the original large field of view may also be applied tomeasurement such as an optical channel for Optical Coherence Tomography,for ophthalmology surgical lasers including but not limited tofemtosecond laser workstations.

Tissue Thickness Measurement Examples

The systems and methods here may be used to measure corneal thickness orother anatomy to prepare a treatment plan for any numerous treatmentssuch as LASIK, PRK, intra stromal lenticular lens incisions, corneareplacement, or any other treatment. By reducing the power of afemtosecond laser from an incision power to a non-incision powers suchas less than 40 milliwatts for example, a backscatter of the laser maybe measured to calculate distances. These distances may be between aninterior boundary and an exterior boundary of a cornea. Such systems andmethods can produce thickness calculations that are accurate to a 1 μmresolution for example.

The thickness measurements may be used for various purposes. Someembodiments may be used to measure other parameters in the eye or otheranatomy. Some embodiments may be used to identify patients or identifythe appropriate eye to treat by comparing calculated eye tissuethickness with previously calculated thicknesses for a specific patientor eye. Some embodiments may be used to ensure a patent's cornea isthick enough to allow incisions and heal correctly. Some embodiments maybe used to measure corneal thickness both before and after treatment.Some embodiments may be used to replace a cornea on a patient needing atransplant.

FIG. 17 shows a simplified diagram of how the laser systems here couldbe used to focus a laser beam at various depths in the eye and capturereflected backscatter from the interior 1710 and exterior surfaces orsides 1712 of a cornea. In the example, the cornea has an interiorboundary or side 1720. The cornea also has an exterior boundary or side1722. By calculating a time it takes for the laser to sweep through thecornea the system may calculate the distance between the cornealboundaries. The system can receive and detect changes in the reflectedbackscatter as the focal point moves from the interior of the eye towardthe surface of the cornea and through the cornea. As the laser focalpoint moves in and through different tissues the beam may scatter andreflect differently. Such energy can be captured by a beam splitter andanalyzed by a detector. The detector may gather information of reflectedpower changes over time as the z axis focus moves from inside theanterior chamber of the eye, through the lens, and through the cornealstroma. A power to time chart may be calculated showing changes or peaksin power when the focus of the laser pulse passes different tissues.

For purposes of simplicity only, no epithelial layer, endothelial layeror other structures are shown in the eye in example in FIG. 17 but anyof these structures could be measured in the same or similar ways.

As shown in FIG. 17, the femtosecond laser patient interface 1702 couldbe used in measuring the corneal thickness in both an applanated ordocked position on the eye as shown in FIG. 17, or free (not shown), asin some distance from the eye. It could be used in a liquid interface aswell (not shown). In some embodiments, the system could adjust orcorrect of the various distances or media the beam travels would need tobe entered in the calculations.

FIG. 18 shows an example system for measuring a cornea 1810 thickness orother tissues. The example shows how the system is able to focus a laserbeam in the z axis and move the focal point of the laser beam in the zaxis to sweep or move through various tissues 1854. For example, bysweeping 1854 the focus of the laser focal point in the z axis directionfrom the interior chamber 1812 of the eye, through the cornea 1810, thesystem is able to detect received power of the reflected backscatter.

In the example, the Femtosecond laser 1820 generates a low power pulsedlaser beam 1822. It should also be noted that the beam need not bepulsed but in pulsed embodiments, individual pulses may be generated sothey may be identified and measured and/or counted by the system. Insuch examples, the detector could be used to identify individuallygenerated pulses and thereby reduce the noise of the back scatteredenergy, to more precisely determine the corneal thickness. In someembodiments, the laser beam may have an NA depth of focus between 0.3and 1.3 NA. Some embodiments may use a laser wavelength between 300 μmand 1200 μm. A preferred embodiment may be 345 μm or 1030 μm. Someembodiments may use a laser power at the focal point below 40 milliwatts or in other words below the photo disruption threshold for theeye, as no incision is intended, merely a backscatter of the energy. Insome embodiments, the laser power at the focal point is between 20 and40 milliwatts.

In FIG. 18, the beam 1822 passes into the Z Control 1830 and then thefocusing optics 1832 of the laser system. The laser beam 1834 enters theeye and is focused in the anterior chamber 1812. From there, the laserbeam focal point is moved or swept along the z axis direction 1854 frominside 1850 outward 1852 at a known speed. The reflected back scatter1840 may then be reflected by a beam splitter 1842 and directed througha confocal aperture 1844 into a detector 1846. The detector 1846 mayreceive the returned backscatter energy and measure the power of theenergy as described in FIG. 19.

It should be noted that in certain example embodiments, the laser andthe beam splitter 1842 could also be polarized. Such polarization may beused to restrict the reflected back scatter and reduce the noise of thedetected power spikes. A circular such as clockwise, counterclockwise,or a linear or other polarization could be used to reduce the noise ofthe received beam and more precisely determine the corneal thickness.

The systems and methods could also be used to measure the depth of othertissue such as the epithelial layer as well as the cornea or any othertissue that would create a reflected backscatter.

FIG. 19 shows an example corresponding energy return graph as measuredin the example detector 1846 from FIG. 18. The energy analyzed by thedetector may be plotted on a graph showing power or energy returns asthe laser focal point is moved or swept from the inside of the eye 1850outward 1852 through the cornea or other tissue. The graph on FIG. 19shows Power 1910 of the received backscatter as a function of Time 1920as received in the example by the detector. The energy return 1930 isplotted in this visual for example purposes only. A visual graph is notnecessary for the system to detect energy anomalies or peaks andcalculate the depth of any tissue such as the cornea. In this example,the resulting received backscatter power from the detector shows a spikein received power 1950 as the focal point is moved or swept from theinterior of the eye and passed through the interior side or boundary ofthe cornea. Another appears when the laser beam focal point passed fromthe corneal stroma 1952 into the epithelial layer or beyond.

Using these two peaks and a known speed of the laser focus point sweepin the Z direction, any kind of computing device can calculate timebetween the power spikes 1950 1952, and thereby the distance 1954between the interior and exterior boundaries or sides of the cornea.

Map of Corneal Thickness

From multiple measurements of the thickness of a cornea in the lateral Aand B directions, a map may be produced representing the cornealthickness which may be used in preparing a treatment plan for anynumerous treatments such as LASIK, PRK, intra stromal lenticular lensincisions, cornea replacement, or any other treatment.

FIG. 20 shows an example map of different corneal thicknesses asmeasured in various parts of the eye. In the example, one type of map isshown, but any kind of map or chart of the measured eye thicknessescould be created broken into any of various regions or zones. Thethicknesses in the various quadrants or areas may be measured andplotted on a map and indicating different calculated thicknesses of thecornea. For example, FIG. 20 shows a thickness of 635 μm at quadrant2020 and a thickness of 665 μm in quadrant 2030. Other areas of the mapmay or may not indicate the thicknesses as the laser progresses inmeasuring various areas.

In some embodiments, a heat map may also be created using any of thevariously plotted thicknesses showing color or shaded areascorresponding to particular thicknesses. In some embodiments,interpolations of measurements may be used to estimate thicknesses ofportions of the cornea which are not directly measured. And kind ofvisualization of the calculated thicknesses may be used.

The measurements may be used to design a treatment plan for a patient,for example, if a cornea is too thin, certain treatments may not befeasible. The measurements may be used to positively identify a patient,to ensure treatment is planned correctly for a particular eye, and/orpatient.

For a map of cornea thickness any number of mapped segments may bemeasured and calculated by the system depending on the treatment anddesired resolution.

Alignment

When a patent prepares for treatment, various measurements andpreparation of the eye may occur. During this preparation, using thesystems and methods here, a corneal thickness map may be calculated. Assuch preparation may occur when the patient is not in the same positionas when the treatment is undertaken, a later alignment of the treatmentdevice may be necessary. For example, the patient may be sitting whenpreparing for treatment but lying down when under treatment. Forexample, the patient may not have anything touching the eye whenpreparing for treatment but have a patient interface pushing or ablatingthe eye during treatment. This may result in deflection of the corneawhile ablated and offset the pupil.

These variations in condition may alter the appearance of the eye ordistort its orientation in the head. Such variations and changes maymisalign the treatment devices as compared to the preparation unless acorrection of the alignment is undertaken.

It is to be assumed that an ablated eye cornea thickness is the same asthe natural unablated eye, and that the interior of the eye absorbs anddeflects the pressure placed on the eye from the docked treatmentdevice. However, the cornea may stretch, move or otherwise deflect whenablated. It is these movements that are calculated in the comparison andcompensated for.

Such correction of the alignment may be made using two or more maps of acorneal thickness for an individual eye, where one map may be made whilea patient is sitting upright in a natural an unablated state preparingfor treatment and the second while laying down when the treatment deviceis docked to the eye in an ablated state. The system may compare the twomaps to correct the alignment of the treatment laser while in thetreatment condition.

Corneal Transplant Examples

Certain embodiments may be used in corneal transplants by measuring fromthe interior toward the surface of the cornea instead of measuring fromthe surface down. This is because when removing cornea for a transplant,it is preferable for the operator to know how much cornea is left on theeye and remove the remainder, than to remove a certain amount of cornea,hoping to arrive at a left over layer that was not directly measured.

Corneal transplants require a section of the cornea to be removed fromthe patient so that section can be replaced. Results may be enhanced forsuch procedures when the amount of cornea removed leaves only a thinlayer on the eye. For example, it may be beneficial to remove all but 50μm of corneal tissue and replace that removed section with a replacementtransplant cornea.

In order to determine how deep to make the cut to remove the corneasection, other systems would use a measurement from an exterior of thecornea and measure down into the cornea to an estimated depth. Then alaser would remove that section of the cornea. This other method allowsthe operator to know the depth of the removed section, but it does notallow the operator to know the depth of the remaining tissue. This othertechnique may result in the remaining tissue being either too thick ortoo thin for desired results. Further, such techniques may get too closeor even damage the cornea endothelium layer on the interior side of thecornea.

Alternatively, using the systems and methods described here may allow aprecise measurement from the interior of the cornea toward the surface,instead of measuring down from the exterior of the cornea, and guessingthe depth to cut. Such methods and systems may allow the laser to makean incision at a known measured distance from the endothelium layer inthe cornea, thus allowing removal of all but a known amount of tissue.

Another embodiment of the systems and methods here may be compensationfor corneal folds which may occur when the system is docked to a patientfor treatment. FIG. 21 shows an example of such corneal folds 2104 thatmay occur when the patient interface (not shown) docks with the cornea2102 of a patient and presses it into a flatter shape as shown in theside view cut-away of FIG. 21. In so docking, the cornea becomesapplanated and possibly distorted by the pressure while pushed into aflatter shape than the cornea in its free state. When the cornea is soflattened, corneal waves, folds, or wrinkles 2104 may result on theanterior side of the cornea. Incising a flat cut 2108 on the cornea inthis state might then result in a distorted cut 2110 when the cornea isreturned to its natural, free and undocked state 2112. This is anundesired effect, and one that can be compensated for using the systemsand methods described here.

FIG. 22 shows an example, similar to FIG. 21 but in this case, where thesystems and methods here are used to correct for corneal wrinkles 2204.As shown in FIG. 21, in FIG. 22, when the cornea 2202 as shown in a sideview cut-away, is applanated or docked by the system, it may result incorneal folds in the anterior side 2204. But using the systems andmethods here, a precise measurement may be made of the anterior cornealfolds 2204 and the system could be used to incise a cut 2208 thatfollows these wrinkles 2204 instead of being flat. The result may be amore uniform or smoother surface 2210 when the cornea 2212 is undockedand returned to its natural state. Such a smoother surface may producebetter results for the patient than by incising a cut as in FIG. 21which does not follow the wrinkles in the anterior applanated cornea.

It should be noted that the wrinkles shown in FIGS. 21 and 22 aresimplistic two dimensional representations of what a corneal fold maylook like. The systems and methods here may be used to measure threedimensional corneal folds or wrinkles, and then incise following thethree dimensional folds or wrinkles. The figures are therefore intendedto be explanatory and not limiting in any way.

All patents and patent applications cited herein are hereby incorporatedby reference in their entirety.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the embodiments (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. The term “connected” is to beconstrued as partly or wholly contained within, attached to, or joinedtogether, even if there is something intervening. Recitation of rangesof values herein are merely intended to serve as a shorthand method ofreferring individually to each separate value falling within the range,unless otherwise indicated herein, and each separate value isincorporated into the specification as if it were individually recitedherein. All methods described herein can be performed in any suitableorder unless otherwise indicated herein or otherwise clearlycontradicted by context. The use of any and all examples, or exemplarylanguage (e.g., “such as”) provided herein, is intended merely to betterilluminate embodiments and does not pose a limitation on the scope ofthe embodiments unless otherwise claimed. No language in thespecification should be construed as indicating any non-claimed elementas essential to the practice of the embodiments.

While certain illustrated embodiments of this disclosure have been shownand described in an exemplary form with a certain degree ofparticularity, those skilled in the art will understand that theembodiments are provided by way of example only, and that variousvariations can be made without departing from the spirit or scope of theembodiments. Thus, it is intended that this disclosure cover allmodifications, alternative constructions, changes, substitutions,variations, as well as the combinations and arrangements of parts,structures, and steps that come within the spirit and scope of theembodiments as generally expressed by the following claims and theirequivalents.

1.-20. (canceled)
 21. A method for incising a cornea of an eye of apatient using a laser system, comprising: docking a patient interface ofthe laser system to the eye; generating a first laser beam using thelaser system, the first laser beam having a power below a photodisruption threshold for the eye; focusing the first laser beam to afocal point in an interior side of the cornea; moving the laser focalpoint in a depth direction of the eye from the interior side of thecornea through the cornea and to an exterior side of the cornea;capturing a backscatter of the laser focal point as it moves in thedepth direction from the interior side of the cornea to the exteriorside of the cornea; recording a power of the captured backscatter as thelaser focal point moves in the depth direction from the interior side ofthe cornea to the exterior side of the cornea; identifying peaks of therecorded power of the captured backscatter; determining a cornealthickness based on the identified peaks of the recorded power, anddetermining an incision depth based on the corneal thickness; generatinga second laser beam using the laser system, the second laser beam havinga power above the photo disruption threshold for the eye; and incisingthe cornea at the incision depth using the second laser beam.
 22. Themethod of claim 21 wherein the incision depth is 50 μm from anendothelium layer of the cornea.
 23. The method of claim 21, furthercomprising determining, from the captured backscatter, a folded shape ofthe cornea while the patient interface is docked; wherein the incisionon the cornea is performed at a cutting distance and follows the foldedshape of the docked cornea.
 24. The method of claim 23, wherein the stepof determining the folded shape of the cornea comprises: moving thefocal point of the first laser beam in a lateral direction perpendicularto the depth direction to a plurality of lateral locations; and with thefocal point at each of the lateral locations, repeating the step ofmoving the laser focal point in the depth direction, the step ofcapturing the backscatter, the step of recording the power of thecaptured backscatter, the step of identifying the peaks, and the step ofdetermining the corneal thickness and the incision depth, to determinethe incision depth corresponding to each of the lateral locations. 25.The method of claim 21 wherein the laser beams have a wavelength between1020 and 1040 nm or between 335 and 400 nm.
 26. The method of claim 21wherein the laser beams have a numerical aperture NA between 0.3 and1.3.
 27. The method of claim 21 wherein the laser beams are pulsed laserbeams having a pulse duration between 10 femtoseconds and 10picoseconds.
 28. An ophthalmic surgical laser system comprising: a lasersystem configured to generate a laser beam; focusing optics configuredto focus the laser beam to a focal point; an xy-scan device configuredto move the focal point of the laser beam in lateral directions; az-scan device configured to move a depth of the focal point of the laserbeam; and a backscatter capture device configured to capture backscatterfrom the focal point of the laser beam; a controller operably coupledwith the laser system, the xy-scan device, the z-scan device, and thebackscatter capture device, wherein the controller is configured to:control the laser system to generate a first laser beam having a powerbelow a photo disruption threshold for the eye; control the z-scandevice to direct a focal point of the first laser beam within apatient's eye at various depths starting at an interior side of a corneaof the eye and moving in a depth direction through the cornea to anexterior side of the cornea; control the backscatter capture device tocapture backscatter from the laser as the laser focal point moves in thedepth direction from the interior side of the cornea to the exteriorside of the cornea; record a power of the captured backscatter as thefocal point moves in the depth direction from the interior side of thecornea to the exterior side of the cornea; identify peaks of therecorded power; determine a corneal thickness based on the identifiedpeaks, and determine an incision depth based on the determined cornealthickness; control the laser system to generate a second laser beamhaving a power above a photo disruption threshold for the eye; andcontrol the xy-scan device and the z-scan device to direct a focal pointof the second laser beam within the eye to incise the cornea at theincision depth.
 29. The system of claim 28 wherein the incision depth is50 μm from an endothelium layer of the cornea.
 30. The system of claim28 wherein the controller is further configured to determine, from thecaptured backscatter, a folded shape of the cornea, and to control thexy-scan device and the z-scan device to incise the cornea at a cuttingdistance following the folded shape of the cornea.
 31. The system ofclaim 30, wherein the controller is configured to determine the foldedshape of the cornea by: controlling the xy-scan device to move the focalpoint of the first laser beam in a lateral direction to a plurality oflateral locations; with the focal point being at each of the laterallocations, repeating the step of controlling the z-scan device to movethe laser focal point in the depth direction, the step of capturing thebackscatter, the step of recording the power of the capturedbackscatter, the step of identifying the peaks, and the step ofdetermining the corneal thickness and the incision location, todetermine the incision depth corresponding to the each of the laterallocations.
 32. The system of claim 28 wherein the laser beams have awavelength between 1020 and 1040 nm or between 335 nm and 400 nm. 33.The system of claim 28 wherein the laser system is configured to producethe pulsed laser beams having a numerical aperture NA between 0.3 and1.3.
 34. The system of claim 28 wherein the laser system is configuredto produce the pulsed laser beams having a pulse duration between 10femtoseconds and 10 picoseconds.
 35. A method for making an incision ina cornea of a patient's eye using a laser system, comprising: dockingthe patient eye to patient interface device of the laser system; whilethe eye is docked, measuring a folded shape of an interior surface ofthe cornea; and while the eye is docked, incising the cornea at acutting distance from the cornea interior surface, wherein the incisionon the cornea at the cutting distance follows the measured folded shapeof the interior surface of the cornea.
 36. The method of claim 35,wherein the step of measuring a folded shape of an interior surface ofthe cornea is performed using a first laser beam generated by the lasersystem, the first laser beam having a power below a photo disruptionthreshold for the eye, and wherein the step of incising the cornea isperformed using a second laser beam generated by the laser system, thesecond laser beam having a power above a photo disruption threshold forthe eye.
 37. The method of claim 36, wherein the step of measuring thefolded shape of the interior surface of the cornea comprises:positioning the focal point the first laser beam at a plurality lateralpositions in an interior side of the cornea; and while the laser focalpoint is at each of the plurality lateral positions: moving the laserfocal point in a depth direction of the eye from the interior side ofthe cornea through the cornea and to an exterior side of the cornea;capturing a backscatter of the laser focal point as it moves in thedepth direction from the interior side of the cornea to the exteriorside of the cornea; recording a power of the captured backscatter as thelaser focal point moves in the depth direction from the interior side ofthe cornea to the exterior side of the cornea; identifying peaks of therecorded power; determining a corneal thickness at the correspondinglateral position based on the identified peaks of the recorded power.38. The method of claim 35 wherein the incision depth is 50 μm from anendothelium layer of the cornea.
 39. The method of claim 35 wherein thelaser beams have a wavelength between 1020 and 1040 nm or between 335and 400 nm.
 40. The method of claim 35 wherein the laser beams arepulsed laser beams having a pulse duration between 10 femtoseconds and10 picoseconds.